serial: imx: fix the wrong number of scatterlist entries when xmit->head is 0

When the (xmit->tail > xmit->head) is true and the xmit->head is 0,
we only need one DMA scatterlist in actually. Current code uses two DMA
scatterlists in this case, this is obviously wrong.

This patch fixes it.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index c6c3b160dac763955d44a788f203fd7a4b4dd42c..cadf7e5848b2421c5b2d80bc39892ab809345a2e 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -532,7 +532,7 @@ static void dma_tx_work(struct work_struct *w)
                return;
        }
 
-       if (xmit->tail > xmit->head) {
+       if (xmit->tail > xmit->head && xmit->head > 0) {
                sport->dma_tx_nents = 2;
                sg_init_table(sgl, 2);
                sg_set_buf(sgl, xmit->buf + xmit->tail,